MB-8131: Add icu dlls to staging area during build

Change-Id: Ia9dc781ed92a8aa2903cd6f3cefe68be275fccec
Reviewed-on: http://review.couchbase.org/25913
Reviewed-by: Sriram Melkote <siri.couchbase@gmail.com>
Tested-by: Bin Cui <bin.cui@gmail.com>